Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Water pathways make fuel cells more efficient

24.09.2015

Researchers from the Paul Scherrer Institute (PSI) have developed a coating technique in the laboratory that could raise the efficiency of fuel cells. The PSI scientists have already applied to patent the technique, which is suitable for mass production.

Researchers from the Paul Scherrer Institute (PSI) have developed a coating technique in the laboratory that could raise the efficiency of fuel cells. Fuel cells generate electricity from hydrogen and oxygen. The gases are transported to the cell’s electrodes from the outside.


This ‘carbon paper’ was made hydophilic along certain paths. That let the gases flow through more quickly.

Paul Scherrer Institut/Markus Fischer

However, on their way to the electrodes, the gases encounter liquid water that is produced constantly in the fuel cell and should flow out of the cell. When too much water accumulates, the gases flow more slowly, thus limiting the generation of electricity.

“Our newly developed coating ensures that the liquid water and the gases flow through the porous materials in the fuel cells using separate channels. This improves the performance and the stability of the fuel cells”, says the head of the study, Pierre Boillat from the Electrochemistry Laboratory at PSI.

Fuel cells convert the chemical energy contained in the gases into electricity. The electricity produced can be used, for example, to power an electric car.

The only chemical product of the reactions taking place in fuel cells is water. The “exhaust gas” of a fuel cell car thus only contains harmless water vapour.

Fuel cell cars ready for series production have been available since 2013. But researchers around the world continue to work on raising the efficiency of fuel cell systems and lowering their costs.

Water limits electricity output

One important aspect of this work is the removal of liquid water from parts of the fuel cells where it is undesired because it disrupts the flow of the gas. For example, water gathers in the pores of what is referred to as the gas diffusion layer, a layer generally consisting of carbon fibre materials, which among other things ensure transportation and fine distribution of the hydrogen and oxygen to the cell’s electrodes. The water that gathers in the gas diffusion layer obstructs the flow of the gases and therefore restricts the power output of the cell.

In commercially available fuel cells, the carbon fibres of the gas diffusion layer are generally coated evenly with a hydrophobic polymer that aims to allow the water to run off more easily. With this coating, the water is distributed arbitrarily in the material, and the gases are often forced to follow tortuous paths through the diffusion layer. As a result, the gases only reach the electrodes slowly, thus reducing the performance of the fuel cells.

The new solution from PSI solves the problem by creating separate “run-off channels” where virtually all of the water collects. In the remaining, dry channels, the gases can then flow more quickly.

A process suitable for mass production

The PSI researchers already knew from earlier experiments that it is not just the amount but also the distribution of the water in the diffusion layer that matters. “Now for the first time we have implemented this idea in a process suitable for mass production”, explains PSI doctoral student Antoni Forner-Cuenca, who carried out the experiments in the laboratory.

The concept of the PSI researchers is to partly turn the original, water-repellent polymer coating into a hydrophilic coating along straight paths. The water is basically sucked into those channels, while the remaining areas of the gas diffusion layer remain mostly dry. The PSI scientists have already applied to patent this process.

In order to create the water channels, the researchers inserted hydrophilic (water attracting) molecules into the structure of the original polymer. First of all, they had to treat the polymer with an electron beam so that it could bond the molecules to be attached.

Electron beam and hydrophilic molecules

This involves transmitting the electron beam through a metal mask or grid to create two distinct areas: In the places where the beam passes through the grid, the original coating can later be changed to create hydrophilic channels. In the places where the beam does not pass through the grid, the original polymer remains hydrophobic.

In the area changed by the electron beam, the original polymer coating reacts chemically with particular molecules that make it become hydrophilic, thereby creating preferential pathways for the liquid water to be removed efficiently.

The process developed at PSI for attaching functional molecules with the help of an electron beam is described by the researchers as “radiation grafting”. It is similar to the grafting process common in gardening whereby valuable plants are grafted onto a foreign but robust stem. In this case, the hydrophilic molecules give the base polymer the desired hydrophilic properties.

The scientists were able to demonstrate that the channels they create do in fact suck almost all of the water into them. By contrast, the other areas remain almost completely dry. The proof was provided by images of the gas diffusion layer that the scientists obtained using neutrons from the ICON beamline of the spallation neutron source SINQ at PSI.

*This work was funded by the Swiss National Science Foundation (SNSF)(project number: 143432).

Text: Paul Scherrer Institute/Leonid Leiva

About PSI
The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of matter and materials, energy and environment and human health. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 1900 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 380 million. (Last updated on April 2015)

A video is available at http://psi.ch/AY9s


Contact

Dr. Pierre Boillat (French, English, German)
Project Head, Neutron Radiography
Electrochemistry Laboratory
Paul Scherrer Institut
Telephone:
E-mail: pierre.boillat@psi.ch

Original publication

Engineered Water Highways in Fuel Cells: Radiation Grafting of Gas Diffusion Layers
Antonio Forner-Cuenca, Johannes Biesdorf, Lorenz Gubler, Per Magnus Kristiansen, Thomas Justus Schmidt, Pierre Boillat
Advanced Materials, 23 September 2015
DOI: 10.1002/adma.201503557

Weitere Informationen:

http://www.psi.ch/lec/electrochemical-energy-conversion

Dagmar Baroke | idw - Informationsdienst Wissenschaft

Further reports about: Fuel cells PSI coating electricity electrodes gases hydrophilic materials polymer coating

More articles from Process Engineering:

nachricht Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht A laser for divers
03.05.2017 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Physicists Design Ultrafocused Pulses

Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.

Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

Programming cells with computer-like logic

27.07.2017 | Life Sciences

Identified the component that allows a lethal bacteria to spread resistance to antibiotics

27.07.2017 | Life Sciences

Malaria Already Endemic in the Mediterranean by the Roman Period

27.07.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>